Sheridan transmission repair customers, the first automatic transmission using hydraulic fluid was developed in 1932 by two Brazilian engineers, José Braz Araripe and Fernando Lehly Lemos; Later, the prototype and the project were sold to General Motors, who introduced the technology in the 1940 Oldsmobile model as a “Hydra-Matic” transmission. However, an article published by the Wall Street Journal credits the German auto parts company ZF Friedrichshafen for the invention, which would have occurred shortly after World War I.
In 1934, both REO and General Motors developed semi-automatic transmissions that were less difficult to operate than a fully manual unit. These designs, however, continued to use a clutch to engage the engine with the transmission. The General Motors unit, dubbed the “Automatic Safety Transmission,” was notable in that it employed a power-shifting planetary gearbox that was hydraulically controlled and was sensitive to road speed, anticipating future development.